Locking devices for washing machines or electromechanical appliances with bimetallic element

ABSTRACT

A safety interlock for the door of electrical appliances such as washing machines comprises a thermostatic element heated by electrical power supplied to the appliance causing it to deflect. The deflection causes a locking member to slide into a mating aperture in a slide plate when the slide plate is biased into position by a hook on the appliance door. Once the locking member is in locking position, the door cannot be opened until the thermostatic element cools after deenergization. Means are provided for preventing excessive deformation of the thermostatic element and a shunt current path is provided to limit the amount of current passing through the thermostatic element and/or heater. Two forms of thermostatic elements and heaters therefor are disclosed.

United States Patent [72] Inventor Norberto Brighenti Naples, Italy [21]App1.No. 783,372

[22] Filed Dec. 12, 1968 [45] Patented Nov. 2, 1971 [73] Assignee TexasInstruments Incorporated Dallas, Tex.

[54] LOCKING DEVICES FOR WASHING MACHINES 0R ELECTROMECHANICALAPPLIANCES WITH BIMETALLIC ELEMENT 8 Claims, 1 1 Drawing Figs.

[52] U.S. Cl 337/77,

[51] Int. Cl H01h27/06,

I-lOlh 61/06 [50] Field of Search ZOO/61.62, 61.63, 6164; 210/149; 3l0/4.1; 337/77, 97, 98, 103

[56] References Cited UNITED STATES PATENTS 3,096,413 7/1963 Gryctko eta1 337/83 IJX 3,458,675 7/1969 Del Gaudio 337/92 X 3,062,937 11/1962Flanagan..... 337/97 X 2,738,072 3/1956 Knight..... 210/149 2,539,185l/l95l Dayton 310/4.1

Primary Examiner-Bernard A. Gilheany Assistant Examiner-Dewill M. MorganAuorneysI-laro1d Levine, Edward J Connors, J r. and John A. I-IaugABSTRACT: A safety interlock for the door of electrical appliances suchas washing machines comprises a thermostatic element heated byelectrical power supplied to the appliance causing it to deflect. Thedeflection causes a locking member to slide into a mating aperture in aslide plate when the slide plate is biased into position by a hook onthe appliance door. Once the locking member is in locking position, thedoor cannot be opened until the thermostatic element cools afterdeenergization. Means are provided for preventing excessive deformationof the thermostatic element and a shunt current path is provided tolimit the amount of current passing through the thermostatic elementand/or heater. Two forms of thermostatic elements and heaters thereforare disclosed.

m a 7 13 10 a l a u i 24 26' I7 24 2a 5 a 5 i PATENTEU m2 m1 SHEET 2 [IF4 in (i LOCKING DEVICES FOR WASHING MACHINES OR ELECTROMECIIANICALAPPLIANCES WITI-I BIMETALLIC ELEMENT The present invention relates to animprovement for safety devices that are mounted for example on washingmachines for the purpose of preventing the opening of the cover duringthe periods in which the motor is running and when the washing machineis in the water-heating phase and of permitting the opening of thecover, in the absence of power, only after a predetermined delay.

As is known, one type of device for locking the cover and releasing itagain after a predetermined time interval is essentially composed of abimetallic element which, through the effect of heat, is deformed,causing movement of a ratchet. This ratchet projects from the device andengages with a fastening device for the cover of the washing machinepreventing it from moving and therefore opening of the cover.

In the absence of power, through the effect of the accumulated heat orthermal inertia, the bimetallic element takes a certain time to cool andthus return the ratchet to the original position in order to allow theopening of the cover.

In these devices the bimetallic element, since it is usually connectedelectrically in series with the machine, is considerably stressed sinceit must intervene both when the machine consumes the minimum power (whenit is in the washing phase) and when it consumes the maximum power (whenit is in the water-heating phase or when it is at the start of thecentrifuging phase. It is therefore necessary to dimension thebimetallic element sufiiciently large and permit it a substantialexpansion or bending so as to avoid permanent deformations. Thisinvariably results in cumbersome devices.

To avoid excessive overall dimensions and to limit the stress on thebimetallic member it has already been suggested to periodicallyinterrupt the electric power for heating the bimetallic element when thelatter has reached a predetermined deformation. In this case, thebimetallic element will, at the maximum power, be strongly stressed onlywhen in cooling down it reestablishes its power supply input and toavoid a permanent deformation it is necessary to permit it a largerdisplacement; consequently, the device will be more cumbersome than isstrictly required under the actual operating conditions.

In general in washing machines where a device according to the inventionfinds special application the space between the basket and the outerplate is reduced to a minimum and therefore the devices which aretherein inserted must be simple and efficiently conserve space.

Other safety means, also in addition to the described devices, are usedfor the purpose of interrupting the power supply of the machine when itslid is open.

In general, switches are used whose control, with appropriateadjustments, is effected by the cover of the washing machine itself.

It is an object of the present invention to provide an inexpensivesafety device, of small dimensions, which is equipped with means forprotecting the bimetallic member against excessive stresses and onewhich can incorporate means for preventing the supply of electric powerto the washer when the cover of the latter is open.

Other objects and features will be in part pointed out hereinafter.

According to the invention, the locking device includes in combination athermostatic or bimetallic element electrically connected in series inthe electrical supply circuit of the apparatus to be protected; theelectrical connection being arranged so as to obtain joulean heating ofthe bimetallic element; means for limiting the deformation of thebimetallic element, means actuated by the bimetallic element for themechanical safety locking of the apparatus to be protected; means forconnecting in parallel with the bimetallic element an electricalresistance element to reduce the current flowing through it. theresistance element being in a heat exchange relation with the bimetallicelement in order to maintain a constant deformation in the presence ofthe electrical load part apparent and in that determines the subsequentdeformation. The apparatus includes further means for interrupting theelectrical supply to the washing machine controlled by a sliding platein such a manner that there is no need for any regulation to be made inthe machine to obtain the deenergization in the position desired for theopening of the cover.

The present invention will now be described with reference to apreferred fonn of the invention which is given only by way of example asshown in the attached drawings, wherein:

FIG. 1 shows the device according to the invention seen along thetransversal section A-A of FIG. 2.

FIG. 2 shows the section B-B of FIG. 1

FIG. 3 shows the device according to the invention in the operatingposition according to the transversal section C-C of FIG. 4.

FIG. 4 shows the section D-D of FIG. 3.

FIG. 5 shows a plan view of the sliding plate.

FIG. 6 shows a device according to a second embodiment of the inventionin the resting position according to the transversal section A-A' ofFIG. 7.

FIG. 7 shows the section B'B' of FIG. 6.

FIG. 8 shows the invention along section c'-c' of FIG. 7.

FIG. 9 shows the device according to the invention in the operatingposition according to the transversal section D'-D' of FIG. 10.

FIG. 10 shows the section 5-5 of FIG. 9.

FIG. 11 shows the plan view of the sliding plate.

Referring to the drawings, as seen in FIG. 2, 4, 7 and I0 terminals land 2 of the locking device are provided for electrical connection inseries with the power supply of the machine to be protected.

In FIGS 1 and 2, the bimetal 3 which is generally U-shaped inconfiguration is shown in the resting position. A first end is fastenedto the terminal I and, the other end is fastened to an elongatedstationary contact arm 4 which also carries contacts 5 and 8. An arm 7extends from terminal 1 in cantilever fashion and is located inunderlying parallel relation to one leg of bimetal 3. One end of aU-shaped elastic lamina 6 of predetermined electrical resistance isfastened to the free end of arm 7 and is located in underlying parallelrelation to the other leg of bimetal 3.

Stationary contact arm 4 and the free end of lamina 6 are provided withcontact elements 8 and 9 respectively which in this condition areelectrically separated.

One end of a flexible lamina member 10 is attached to the central brightportion of the bimetal 3 with the other end of member 10 engaging inslot 11 of ratchet 12. Also mounted on the bight portion of bimetal 3and interposed between member 10 and lamina 6 is an insulating button13. The ratchet I2 is slidable in slots 14 and 15 of the cover 16 andbox 17 respectively. p I

Terminal 2 ends in a contact extension 18 on which, by means of a spring19, the movable contact 20 is supported. The spring 19 is linked to aslide 21 which engages in the slot 23 of sliding plate 24.

The cover 16 and box 17 are locked by means of any con ventional joiningmembers 25 on the fixed plate 26.

Between the box 17 and the plate 26 moves the sliding plate 24 which iscontrolled as it is shown in FIG. 3 by the hooking member 27 of thewashing machine.

Spring 28 located in opening 29 returns the sliding plate 24 to theposition of FIGS. 1 and 2 when the lid of the washing machine is open.

When the lid of the washing machine is closed hooking member 27 causessliding plate 24 to move into the position shown in FIGS. 3 and 4.

During this movement the plate 24 entrains the slide 21 and thus thespring 19 which in passing beyond the position of the extension 18forces the movable contact 20 to move from the position shown in FIG. 2to that shown in FIG. 4 and thus make theelectrical contact so that themachine is able to function.

As can be seen from FIG. 2, it is possible to insert in the device othercontacts 30 which can serve to obtain the opening of all the powerlineswhich supply the machine.

When the motor of the washing machine starts to run the bimetal, throughthe joulean effect, deforms itself and moves the ratchet 12 from theposition shown in FIG. 1 to that of FIG. 3. In this position the ratchet12 is inserted in the slot 22 of the sliding plate 24.

In this position the plate 24 cannot make further movements thuspreventing a clearing of the hooking member 27.

During its movement the bimetal pushes, with the insulating button 13,the resistance 6 until the contact 9 bearing on the contact 8 connects,in parallel with the bimetal, the resistance 6. At this moment thecurrent subdivides between the resistance 6 and the bimetal to such anextent that through the latter passes only a small part of the current.That is, when button 13 transmits the motion of bimetal 3 to effectclosing of contacts 8 and 9, the current will flow from terminal 1either through bimetal 3 to stationary contact arm 4, or through arm 7,lamina 6, contacts 9 and 8 to stationary contact arm 4 and thence tostationary contact 5, movable contact 20, extension 18 to terminal 2.

When the washing machine draws a heavy current the bimetal is maintainedconstantly in the position of FIG. 3 by the joulean effect of the smallcurrent running through it and by the heat which is imparted to itthrough radiation of the resistance 6.

If a strong current were suddenly to pass through the device it wouldcause the bimetal in response to 2R heating and after the operatingposition has been reached to move even beyond that point. However, inaccordance with the invention, its thrust would be cushioned by theelastic members 6 and 10 which would hinder it from deforming itselfpermanently.

In some machines wherein the vibrations are very substantial and inorder to prevent vibrations from opening the electrical contact 8-9resulting in the bimetal carrying the whole amount of current, theratchet 12 may be provided with a small magnet 31. When the ratchet 12is in the position of FIG. 3 it is attracted toward the plates 24 and 26which are made of magnetic material thus conferring an added force uponthe contact 8-9 such that it affords a sufficient stability to resistthe effects caused by the vibrations. When the bimetal cools down theelastic force stored up during its movement separates the magnet thusreturning the ratchet 12 to the position ofFIG. 1.

When the machine has finished the washing cycle or when there is asudden lack of power the bimetal cools down within a predeterminedsafety period so as to permit the opening of the lid only when therotating basket has stopped. L

Turning noL to FIGS. 6-11, a modification of Lthe invention is shown. Asin the FIGS. 1-5 embodiments, the locking device is connectedelectrically in series with a power supply of the machine by means ofconnectors 101 and 102.

In FIGS. 6 and 7, bimetal 103, shown in the resting position, isfastened to the terminal 101 at one end.

On the second end 118 of bimetal 103 is fastened resistance 104 which iswound around the bimetal and around the plate 105 that has the purposeof electrically and thermally insulating bimetal 103.

Also on end 118 of bimetal 103 is fastened an elastic lamina 106 whichengages in slot 107 of ratchet 108.

Ratchet 108 is slidably mounted in slot 109 of the insulating case 110and is pressed by the lamina 106 against the inner wall of the cover111.

The second end of the resistance 104 is fastened to the platelet 112 towhich are fastened the line contact 113 and short-circuitlng contact114.

This contact is located on the attachment 115 of the small plate 112 onwhich is made a threaded hold 116 which engages the screw 117 that islocated between the walls of screw 111 and case 110.

Screw 117, when turned, deforms the attachment 115 and thereforedetermines the movement of the contact 114.

As a result, there is obtained the adjustment of contact 114 and a shuntcircuit contact 120 described below.

On terminal 101 is fastened the elastic lamina 119 having apredetermined electrical resistance as a function of the particularheating desired and of the current running through it.

At the center of the lamina 119 is fastened the short circuit contact120. Terminal 102 ends with the contact attachment 121 on which, bymeans of spring 122, the movable contact 123 is supported. The spring122 is connected to the slide 124 which engages in the slot 125 of thesliding plate 126.

The cover 111 and the case 110 are locked by conventional joiningmembers 127 on the fixed plate 128.

Between case 110 and plate 128 moves sliding plate 126 which isoperated, in FIG. 9, by hooking member 129 of the washing machine. L

Spring 130 located in slot 131 returns sliding plate 126 to the positionshown in FIGS. 6 and 7 when the lid of the washing machine is open.

When the lid of the washing machine is being closed member 129 operatesplate 126 which moves from the position of FIGS. 6 and 7 and to theposition of FIGS. 9 and 10.

During this movement plate 126 pulls along slide 124 and thus spring 122which, in passing beyond the position of extension 121, forces movablecontact 123 to move from the position shown in FIG. 7 to that of FIG. 10thus making electrical contact for the machine to be able to function.When the washing machine or other appliance is in any washing oroperating phase, the bimetal L103, through the joulean efiect, deformsitself moving ratchet 108 from the position of FIG. 6 to that of theFIG. 9.

In this position since ratchet 108 is in slot 132 of plate 126, theplate is not able to make further movements and therefore prevents therelease of the hooking member 129 of the lid of the washing machine.

During the phase of its movement bimetal 103 pushed the end part of theelastic resistive plate 119 until contact 120 bears on contact 114 andconnects resistance 104 in parallel with the resistive section of theelastic lamina 119.

At this moment, the current subdivides between the resistance 104 andlamina 119 in such a way that only a small part of the current will passthrough the resistance 104.

The movement of the contact 114 through the screw 117 determines avariation of the displacement of the bimetal 103 which permits aregulation of the periods of intervention of the device.

If the device were suddenly traversed by a strong current and thebimetal, to get rid of the accumulated heat, would have to move beyondits operating position; once the said operating position has beenreached. Its thrust would be cushioned by the elastic members 106 and119 which would hinder it from deforming itself permanently.

In view of the above it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

It is to be understood that the invention is not limited in itsapplication to the details of construction and arrangement of partsillustrated in the accompanying drawings, since the invention is capableof other embodiments and of being practiced or carried out in variousways. Also, it is to be understood that the phraseology or terminologyemployed herein is for the purpose of description and not of limitation.

As many changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description as shown in the accompanyingdrawings, shall be interpreted as illustrative and not in a limitingsense, and it is also intended that the appended claims shall cover allsuch equivalent variations as come within the true spirit and scope ofthe invention.

I claim:

1. In an electrical apparatus having an access door, a safety interlockcomprising:

a housing;

a locking member movably mounted in the housing and movable into and outof locking position;

means for moving the locking member into and out of locking position,the means including a thermostatic element which upon deflection causesLmovement of the locking member;

a current path for energizing the interlock, the path including thethermostatic element;

means for partially shunting a portion of the current path around thethermostatic element upon energization of the interlock and apredetermined deflection of the thermostatic element;

a slide plate mounted in the housing, the plate provided with a camsurface adapted to be engaged by a member on the door of the appliance,the slide plate slidable when cammed;

a stationary contact mounted in the housing;

a movable contact arm mounted in the housing and adapted to move intoand out of engagement with the stationary contact, the contact andcontact arm included aselements in the current path; and

means to move the movable contact arm into and out of engagement uponsliding movement of the slide plate.

' 2. A safety interlock according to claim 1 in which the thermostaticelement is a generally U-shaped bimetallic member and a spring elementconnects the bight portion of the bimetallic member to the lockingmember.

3. A safety interlock according to claim 3 in which a magnetic elementis located within the locking member.

4. A safety interlock according to claim 1 in which the movable arm ispivotally mounted and means are provided from biasing the movablecontact arm against the pivotal mount, the means movable from one sideof the pivot to another side upon movement of the slide plate to causemovement of the contact arm.

5. A safety interlock according to claim 1 in which a plurality ofswitches are provided in the housing; and the slide plate is adapted toactuate and deactuate the switches upon movement thereof.L L

6. In an electrical apparatus having an access door, a safety interlockcomprising:

a housing;

a locking member movably mounted in the housing and movable into and outof locking position;

means for moving the locking member into and out of locking position,the means including a thermostatic element which upon deflection causesmovement of the locking member, the thermostatic element being agenerally U-shaped bimetallic member and a spring element connects thebight portion of the bimetallic member to the locking member;

a current path for energizing the interlock, the path including thethennostatic element;

means for partially shunting a portion of the current path around thethermostatic element upon energization of the interlock and apredetermined deflection of the thermostatic element including agenerally U-shaped flexible resistor placed in parallel face-to-facerelation with the bimetallic member;

a shunting contact mounted on a free end of the resistor and movableinto and out of engagement with a stationary shunting contact; and

a motion transfer button mounted on the bight portion of the bimetallicmember adapted on deflection of the bimetallic member to bias theresistor to cause the shunting contact to engage the stationary shuntingcontact. X

7. In an electrical apparatus having an access door, a safety interlockcomprising:

a housing;

a locking member movably mounted in the housing and movable into and outof locking position;

means for moving the locking member into and out of locking position,the means including a thermostatic element which upon deflection causesmovement of the locking member;

a curren path for energizing the interlock, the path Including thethermostatic element;

a terminal; the thermostatic element being an elongated member fixed tothe terminal on an end thereof;

a heater serially connected to the member and in heat transfer relationthereto;

a flexible member connected to another end of the elongated Xmember andLalso to the locking member;

means for partially shunting a portion of the current path around thethermostatic element upon energization of the interlock and apredetermined deflection of the thermostatic element including anelongated shunt resistor attached on an end thereof to the terminal,another end of the shunt resistor attached to the flexible member;

a stationary shunt contact mounted in the housing; and

a movable shunt contact mounted on the shunt resistor and adapted tomove into and out of engagement with the stationary shunt contact uponmovement of the elongated member.

8. A safety interlock according to claim 7 including means to adjust theposition of the stationary shunt contact.

i t l 3

1. In an electrical apparatus having an access door, a safety interlockcomprising: a housing; a locking member movably mounted in the housingand movable into and out of locking position; means for moving thelocking member into and out of locking position, the means including athermostatic element which upon deflection causes movement of thelocking member; a current path for energizing the interlock, the pathincluding the thermostatic element; means for partially shunting aportion of the current path around the thermostatic element uponenergization of the interlock and a predetermined deflection of thethermostatic element; a slide plate mounted in the housing, the plateprovided with a cam surface adapted to be engaged by a member on thedoor of the appliance, the slide plate slidable when cammed; astationary contact mounted in the housing; a movable contact arm mountedin the housing and adapted to move into and out of engagement with thestationary contact, the contact and contact arm included as elements inthe current path; and means to move the movable contact arm into and outof engagement upon sliding movement of the slide plate.
 2. A safetyinterlock according to claim 1 in which the thermostatic element is agenerally U-shaped bimetallic member and a spring element connects thebight portion of the bimetallic member to the locking member.
 3. Asafety interlock according to claim 3 in which a magnetic element islocated within the locking member.
 4. A safety interlock according toclaim 1 in which the movable arm is pivotally mounted and means areprovided from biasing the movable contact arm against the pivotal mount,the means movable from one side of the pivot to another side uponmovement of the slide plate to cause movement of the contact arm.
 5. Asafety interlock according to claim 1 in which a plurality of switchesare provided in the housing; and the slide plate is adapted to actuateand deactuate the switches upon movement thereof.
 6. In an electricalapparatus having an access door, a safety interlock comprising: ahousing; a locking member movably mounted in the housing and movableinto and out of locking position; means for moving the locking memberinto and out of locking position, the means including a thermostaticelement which upon deflection causes movement of the locking member, thethermostatic element being a generally U-shaped bimetallic member and aspring element connects the bight portion of the bimetallic member tothe locking member; a current path foR energizing the interlock, thepath including the thermostatic element; means for partially shunting aportion of the current path around the thermostatic element uponenergization of the interlock and a predetermined deflection of thethermostatic element including a generally U-shaped flexible resistorplaced in parallel face-to-face relation with the bimetallic member; ashunting contact mounted on a free end of the resistor and movable intoand out of engagement with a stationary shunting contact; and a motiontransfer button mounted on the bight portion of the bimetallic memberadapted on deflection of the bimetallic member to bias the resistor tocause the shunting contact to engage the stationary shunting contact. 7.In an electrical apparatus having an access door, a safety interlockcomprising: a housing; a locking member movably mounted in the housingand movable into and out of locking position; means for moving thelocking member into and out of locking position, the means including athermostatic element which upon deflection causes movement of thelocking member; a current path for energizing the interlock, the pathincluding the thermostatic element; a terminal; the thermostatic elementbeing an elongated member fixed to the terminal on an end thereof; aheater serially connected to the member and in heat transfer relationthereto; a flexible member connected to another end of the elongatedmember and also to the locking member; means for partially shunting aportion of the current path around the thermostatic element uponenergization of the interlock and a predetermined deflection of thethermostatic element including an elongated shunt resistor attached onan end thereof to the terminal, another end of the shunt resistorattached to the flexible member; a stationary shunt contact mounted inthe housing; and a movable shunt contact mounted on the shunt resistorand adapted to move into and out of engagement with the stationary shuntcontact upon movement of the elongated member.
 8. A safety interlockaccording to claim 7 including means to adjust the position of thestationary shunt contact.